multi vs one prediction using Regression
I think the model will have no problem taking a multicolumn input. In fact, from your code, this is exactly how you trained it. It expects an input of size [k, 6], where k is k>=1.

Instead you are feeding it with [k, 1] sized data, which are the dimensions of y. So you if you run it like this it should work:

regressionModel.predict(X)